Abstract

Accurate and efficient prediction of melting points for complex molecules is still a challenging task for molecular simulation, although many methods have been developed. Four melting point computational methods, including one free energy-based method (the pseudo-supercritical path (PSCP) method) and three direct methods (two interface-based methods and the voids method) were applied to argon and a widely studied ionic liquid 1-n-butyl-3-methylimidazolium chloride ([BMIM][Cl]). The performance of each method was compared systematically. All the methods under study reproduce the argon experimental melting point with reasonable accuracy. For [BMIM][Cl], the melting point was computed to be 320 K using a revised PSCP procedure, which agrees with the experimental value 337–339 K very well. However, large errors were observed in the computed results using the direct methods, suggesting that these methods are inappropriate for large molecules with sluggish dynamics. The strengths and weaknesses of each method are discussed.

Received 25 January 2012Accepted 26 March 2012Published online 13 April 2012

Acknowledgments:

This material is based upon work supported by the Air Force Office of Scientific Research under AFOSR (Award No. FA9550-10-1-0244) and by the Advanced Research Projects Agency - Energy (ARPA-E), (U.S.) Department of Energy (Award No. DE-AR0000094). Computational resources were provided by the Center for Research Computing (CRC) at the University of Notre Dame. We thank Dr. Saivenkataraman Jayaraman for his help in setting up the PSCP simulations.